Family doctors have been told to look out for scarlet fever as the once feared Victorian disease has made an alarming comeback.

Primary schools across Britain are being hit by the disease as the numbers of children being infected by the bug have hit a 50-year high.

Outbreaks of the highly contagious disease have risen steeply – with 6,157 new cases since September according to Public Health England.

The figures show that 17,586 cases were reported in England in 2015, the highest total since 1967.

This compares with only 1,678 in 2005.

Health officials are unclear as to why scarlet fever has suddenly returned and blame ‘long-term natural cycles’.

But researchers in America, where cases are also on the rise, have linked it to a super-resistant and aggressive strain of bacteria.

One school, St Michael’s Junior School in Bowthorpe Norwich was particularly hard hit with 12 children off sick earlier this month.

Helen Newell, the school’s head said of the outbreak: ‘I think parents are naturally going to be worried about it – it’s your child.

If you know there’s been an outbreak in Bowthorpe, they are going to be worried, but we are really trying to be hyper-vigilant, and if a child is looking unwell we are taking their temperature and looking out for them. With our deep clean, we are not leaving anything to chance.

Other schools are posting warnings on social media.

A primary school in Grimsby, Great Coates, earlier this week issued a letter to parents, and posted a warning on Facebook that the school had suffered an outbreak of the illness telling parents ‘another child in the school has scarlet fever’.

Scarlet fever was very common in the 19th and early 20th centuries but cases dramatically reduced during the last century, partly due to better hygiene.

Health officials are unclear as to why it has suddenly returned and blame ‘long- term natural cycles’.

Dr Theresa Lamagni, Public Health England’s head of streptococcal infection surveillance, said: ‘Parents can play a key role in recognising when their child needs to be seen by their GP.

‘Early signs to look out for are sore throat, headache and fever with the characteristic pinkish/red sandpapery rash appearing within a day or two, typically on the chest and stomach but then spreading to other parts of the body.

‘Individuals who think they or their child may have scarlet fever should seek advice from their GP without delay as prompt antibiotic treatment is needed.

‘Symptoms usually clear up after a week and the majority of cases will resolve without complication as long as the recommended course of antibiotics is completed.’

Potential complications include ear infection, throat abscess and pneumonia. Patients who do not show signs of improvement within a few days of starting treatment should seek urgent medical advice, PHE advised.

Experts say the disease was far more deadly in the Victorian era as it was caused by a different strain of bacteria, which was later eradicated. During the period there were around 100,000 cases a year and up to 20,000 deaths.

Dr Lamagni said: ‘There’s no suggestion what we are seeing now is anything like during the Victorian era. Scarlet fever itself isn’t serious. We are not worried in the sense that we are likely to see a lot of problems – but it is of concern because this bacteria can be nasty for some people.’

She advised parents to look out for a rash, usually starting on the back, a temperature and the child complaining of headache and nausea.

‘Look out for symptoms and if the child has got these symptoms, go and see your GP,’ she said. ‘If you are given antibiotics, make sure you finish them.’

The disease is caused by the bacteria group A streptococcus and is spread through coughs and sneezes or touching contaminated objects.

In most cases it clears up by itself but GPs may prescribe penicillin if symptoms are particularly nasty or there is a risk of complications.

Scarlet fever usually develops after a sore throat or a skin infection caused by the same bacteria